Now to unlock your jailbroken iPhone using ultrasnow, follow these steps:

Start "Cydia" on your iPhone.

Touch on "Manage" tab on the bottom.

Now touch on "Sources" as seen in the screenshot below:

Note: T-Mobile users should disable 3G before installing ultrasn0w.

Touch on "Edit" and then on "Add". You will be prompted to enter a url source as seen in the screenshot below. Type "http://repo666.ultrasn0w.com" and touch on "Add Source"

Cydia will now automatically update your sources by following a series of automated steps

After installation is completed. Search for "ultrasnow" in Cydia and install this application (T-Mobile users should disable 3G before installing ultrasnow). The lastest version of this app (0.92) will automatically unlock your iPhone so that you can use it with any carrier.

That's all. Just restart your phone and you are good to go. Now, you should have fully unlocked and jailbroken iPhone firmware 3.1.3 on your iPhone 3G or 3GS

NOTE: Please try this at your own risk, we haven't tried this procedure ourselves. You might want to wait for official tools to be released by Dev-Team and Geo-Hotz.